The electronic device fabrication industry requires various liquid chemicals as raw materials or precursors to fabricate integrated circuits, wafers, and other electronic devices. The purity of the chemicals that are used in these applications must be very high in order to meet the stringent requirements of the electronic fabrication industry.
A portion of the efforts used to provide high purity chemicals goes into the design and structure of the containers and systems which deliver these chemicals to the reactor or furnaces where the electronic devices are being fabricated. The purity of the chemicals can deteriorate over time due to thermal decomposition, physical agitation, or chemical reaction with oxygen, moisture, or other contaminants located within the system. It is therefore desirable to periodically in-situ clean the chemical containers with cleaning agent or solvent and a purge gas. However, the solvent itself can serve as a contaminant during the fabrication process if not removed completely from the chemical container before processing chemicals are reintroduced. Therefore, it is desirable to evacuate as much of the solvent as possible from the chemical container after the cleaning process.
In addition, it is important to monitor the quantity of high purity chemical available in the container during its use in the electronic device fabrication process to ensure that enough chemical is available for batch processing and/or fabrication of the wafers. Because the high purity chemicals used in the fabrication process are very expensive, it is desirable to consume as much of the chemical as possible prior to conducting a cleaning cycle. However, it is also important to not empty the chemical container completely, because without leaving any residual chemical (i.e., heals) in the container, the electronic device fabrication process can operate in a run-dry condition, which can result in wafer defects and costly reductions in product yields. Therefore, careful monitoring of the quantity of remaining chemical in the chemical container is desirable.
Various attempts have been made in the prior art to address the issues of purity and monitoring of the quantity of chemicals available for use in chemical containers.
Some known prior art references disclose chemical containers comprising inlet and outlet valves and a diptube, but do not teach a level sensor probe or any means to measure the quantity of chemical remaining in the container.
Another known prior art reference discloses a chemical container with a diptube and an internal float level sensor.
Another known prior art reference discloses a chemical container with a rounded floor and a diptube.
Yet another known prior art reference discloses a chemical container with inlet and outlet valves, a diptube comprising a bend, and a chemical level sensor probe, but in this reference the base portion of the container has a rounded floor and the diptube does not make contact with the floor of the base portion.
There is a need to address the shortcomings of the prior art in addressing the goals of chemical purity, chemical quantity monitoring, and efficient chemical utilization.